logic · 2–5 minutes
Hidden Rule
Belongs or doesn't belong? Find the rule.
Start at
> Level 1: One feature: shape, shade, size or count. Streak of 4
No runs yet
Belongs
Doesn't
How to play
- 01A secret rule decides which cards belong. Two cards that belong and two that don't are shown to start.
- 02New cards arrive one at a time. Sort each one: Belongs (left) or Doesn't (right). Tap a button, swipe the card, or use the arrow keys.
- 03Every sorted card joins its true column, right or wrong, so the evidence keeps growing.
- 04Sort a streak of cards right in a row to clear the level: 4 at first, up to 7. A wrong answer resets the streak.
- 05Only the clock can lose the level. Guessing won't get a streak in time, so find the rule.
- 06When the level ends, the rule is revealed.
Levels
- 1–20 · Beginner
- One feature: shape, shade, size or count. Streak of 4
- 21–40 · Focused
- Comparisons, order and hollow pieces. Streak of 5
- 41–60 · Sharp (Plus)
- Two-part rules, pieces that face a way. Streak of 6
- 61–80 · Expert (Plus)
- Exceptions, neighbors and negations. Streak of 7
- 81+ · Master (Plus)
- The deepest rules and the closest misses. Streak of 7
About
Hidden Rule is a logic game about induction: forming a rule from examples, then testing it on the next card. Every rule comes from a library of 40 handwritten rule families, and every level is dealt fresh.
Each deck is built so that, within its first dozen cards, the hidden rule is the only rule in the library that explains every card. You're never left with two answers that both fit.
Early rules look at one feature, like shape or size. Later ones compare, combine and make exceptions, and the cards get busier: hollow pieces, then pieces that face left or right.
Tips
- > Start with the simplest difference between the two columns. Most rules at a band are only one idea deep.
- > Compare a card with its near twin in the other column. What changed is what the rule cares about.
- > Count things: pieces, shapes, shades. Many rules are about how many.
- > When you get one wrong, look at where it landed. That card is the best clue you have.
- > Don't forget order. Some rules care about the leftmost piece, the ends, or neighbors.
FAQ
Can more than one rule fit?
Early on, yes: that's the puzzle. Each deck is built so that after the first dozen cards, only the hidden rule in the library still fits every card.
Does a wrong answer cost a life?
No. It resets your streak, and the card still lands in its true column to teach you. Only running out of time loses the level.
Is it free?
Yes. Every level is free to play in your browser, with no account and nothing to download.